In the fabrication of semiconductor devices, a semi-conducting wafer must be processed in a large number of processing steps for producing various integrated circuits on chips. These processing steps may amount to as many as several hundred. The various processing steps are conducted in a large variety of processing machines for carrying out chemical or physical reactions on the semi-conducting wafer. In the various fabrication steps, a large number of reactant gases are used. The reactant gases and their reaction products frequently encountered in the semiconductor fabrication industry may be highly flammable. For instance, the highly flammable gases may include silane, hydrogen and various other hydrocarbon gases. An effluent gas from the process machine must therefore be treated either in a chemical process or in a physical absorption or condensation process before it is released into a factory exhaust system and subsequently into the atmosphere.
The high flammability gases, which are normally of high boiling temperature or high boiling temperature components of other gases, present a serious processing hazard in the semiconductor fabrication facility. When such flammable gases are inadvertently, or accidentally ignited either in the chamber of a process machine or in a conduit connecting between the chamber and a flammable gas supply source, extremely serious consequences can result from such mishaps. Major fires have occurred in recent years in semiconductor fabrication facilities which result in serious personal injuries and equipment losses leading to a complete shut-down of the fabrication facility. The inadvertent or accidental ignition of a highly flammable gas can be caused by static electric charges, sparks produced by moving mechanical components or the self-igniting of flammable gases when exposed to high temperatures or oxygen environment.
The flammable gases that pose serious fire hazard may include those which are used as reactant gases and those which are by-products of a chemical reaction occurring in a reaction chamber. Since the exhaust conduits for the individual process machines are normally connected to a single factory exhaust, i.e., all the exhaust conduits from the various process machines are interconnected together in a fabrication facility, the spread of fire or explosion in the conduits can be extremely rapid and wide spread. For instance, a single fire started in a process machine can spread almost instantly to a large number of process machines and gas conveying conduits. The extent of damage to a semiconductor fabrication plant caused by a single fire started in a conduit or in a process machine can be astronomical as measured by the loss of human lives, bodily injuries and property damages.
After the occurrence of a fire in a fabrication facility, the recovery or clean-up procedure can be extremely laborious and time consuming. This is because the large amount of contaminating particles and debris generated during the fire which contaminates all the gas conveying conduits and the process chambers. It is not unusual that, after a major fire has erupted in a semiconductor fabrication facility, at least several months of production time is lost due to the clean-up and the refurbishing of damaged equipment.
It is therefore an object of the present invention to provide an apparatus and a method for detecting ignited flammable gas in a conduit or from a process machine that does not have the drawbacks and shortcomings of the conventional apparatus and methods.
It is another object of the present invention to provide an apparatus for detecting ignited flammable gas in a conduit by utilizing a sensor body equipped with at least one perforated isolator plate for slowing down the flow of an ignited flammable gas.
It is a further object of the present invention to provide an apparatus for detecting ignited flammable gas in a conduit by using a sensor body and at least one perforated isolator plate installed therein wherein both the body and the plate are fabricated of a corrosion-proof material.
It is another further object of the present invention to provide an apparatus for detecting ignited flammable gas in a conduit by using at least one fiber-optical sensor mounted at a gas inlet of a sensor body for sensing an ignited flammable gas in the cavity of the sensor body.
It is still another object of the present invention to provide an apparatus for detecting ignited flammable gas in a conduit by utilizing at least one fiber-optical sensor capable of detecting visible light, IR and UV emissions.
It is yet another object of the present invention to provide an apparatus for monitoring the composition of a gas in a conduit by using a sensor body equipped with at least one perforated isolator plate such that the flow of the gas can be slowed for detection by at least one optical sensor mounted at a gas inlet for the sensor body.
It is still another further object of the present invention to provide a method for detecting ignited flammable gas in a conduit by first providing a sensor body, flowing a flammable gas into the sensor body, mounting at least one optical sensor in the sensor body and sensing an ignited flammable gas in the cavity of the sensor body.
It is yet another further object of the present invention to provide a method for detecting ignited flammable gas in a conduit by first detecting an ignited flammable gas in a cavity of a sensor body by at least one optical sensor, and then sending a signal to a controller for stopping the flow of the flammable gas when ignited flammable gas is detected.